Self-locking screw-thread.



IRVING c. wooDWARD, or cHIcAGo, ILLINOIS.

our.

i SELF-LOCKING SCREW-THREAD.,

To all whom t may concern: t

Be it known that I, IRvING C. WOoDWARn, a citizen of the United States of America, anda resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Self-Locking Screw-Threads, of which the following is a specification: I

T his invention relates to self-locking screw threads of the character described in Patent No.-1,250,748, of December 18, 1917. The type of thread described in said patent' is the standard V thread having a uniform cross sectional area, but with the apex of the thread slightly offset from the center line of the thread. The purpose of so uniformly offsetting'the apex of the thread was to cause it to resiliently or frictionally engage a coacting thread by said coacting vthread forcing the apex toward normal relation'ship with the body of the thread. The purposes of the present invention are the same as those of the prior invention, being to provide an improved form of thread which is self-locking to secure a nut in any position on'a bolt regardless of the pressure between the nutv and the part which is to be retained in place on the bolt, and to provide locking threads which are 'uniform in cross sectional area andare of uniform pitch, and which' may be out by the same operations which are employed to cut .the well-known forms of non-locking threads. The present invention differs from the aforementioned prior invention in that instead of offsetting the. apex-of the thread, the thread is so cut that its base isslightly out of normal position. Thus, such a thread when coacting with a normal thread forces the apex of the normal thread slightly to one side, and in this mannen causes the.

threads .to frictionally engage each other and form a substantially `locked arrangement.

An illustrativeembodiment of the invention is shownin the accompanying drawings, in which- Figure l is a sectional view of the nut. Fig. 2 is an enlarged cross sectional viewA of the improved thread. t

The advantages of the present construction over many other forms of self-locking strength of a standard V thread is not affected by the improved design, and mayA have `the usual uniform pitch and requires but a single operation Specification of Letters Patent.

`of a center line Patented apr. i5, Iain.

. Application led July 12, 1918. Seral No. 244,590.

or die,

in cutting and may be cut by a tp ers from which only in a minute degree di normal .taps and dies.

In the construction shown, the interfitting orcoacting threads on the nut or bolt are of practically equal cross sectional area as standard threads andare formed to provide a snug fit along their `entire surface in the same manner as do the standard forms of threads now commonly in use.

The sole difference of the present invention and the well-known standard threads is that onethread of a pair of coacting threads has its base slightly to one side vof the thread. 'A thread so formed when coacting with a normal thread serves to force slightly to one side the apex of the coacting thread and accordingly effect a passing through the apex' resilient and more or less locking engagel ment between the two threads.

-In the drawing, a bolt l is shown provided with the well-known form of V thread 2, while the nut 3 has a thread 4 so cut as to be practically equal Yin cross sectional area tothe thread 2, but withits base so formed that its center 6 to one side of the center line 7 vpassing through the middle of the apex of the thread. This view of the" drawing for the sake of clearness exaggerates the osetting of the base of the thread, the appearance of the actual thread being not perceptibly different from the appearance of a normal V thread. y

According to the above the threads2 and 4 are uniform in pitch, height and width at the base and are also uniform in cross sectional area, the only difference being that one thread has a base which is not in quite true relation to the vapex of the thread.

The invention may be applied to threads having sharp, flat or rounded apices, but in all cases the thread isl of substantially that form generally approvedV and generally in use and not differing therefrom in extent of bearing area.

When the nut is applied to the bolt, the thread fl .of the nut causes the apex of the thread 2 to be resiliently forced slightly to oneI side, and thus effect the desired frict tional engagement between the' threads.

ous/details of\the construction shown may (Fig. 3) is slightly be altered or omitted without departing from the spirit of this invention as defined by the following claims:

I claim:

l. A threaded member, the thread of which is of uniform pitch andl has sides extending at equal angles from the apex of the thread, except that at the baseor root of the thread the sides slope inwardly on one side, and outwardly on the opposite side from the normal angle.

2. A pair of complementary threaded members, one having a standard thread of equilateral triangular cross-section, and the other having a thread of equal cross Sectional arca and of like triangular form,

except that at the base of the thread the sides slope inwardly on one side, and outwardly on the opposite side from the normal angle.

3. A pair of complementary threaded members, one having a standard thread of triangular cross-Section, dand the other having a thread of equal cross Sectional area and of like triangular form, except that at the base of the thread the sides slope in.- wardly on one side, and outwardly on the opposite side from the normal angle.

Signed at Chicago this 8th day of July, 1918. v

IRVING o'. wooDwARD. 

